Removal of fluoride ions from aqueous solution by the calcination product of Mg–Al–Fe hydrotalcite-like compound

The calcination product of Mg–Al–Fe hydrotalcite compound at 500 °C (HTlc500) was used as the adsorbent to remove fluoride ions from aqueous solution, while the Mg–Al–Fe hydrotalcite compound was synthesized by co-precipitation method. The hydrotalcite-like compounds (HTlcs) were characterized by XRD, FT-IR, TG-DTA, SEM, TEM, BET and pHPZC analysis. The characteristics showed that the HTlc500 had a porous structure, while the Mg–Al–Fe hydrotalcite has a “memory effect”. Batch adsorption studies were conducted under various equilibration conditions, such as different pH, calcined temperature, adsorbent dose, co-existing anions, contact time and initial fluoride ions concentrations. It was found that the HTlc500 had the largest adsorption capacity of 14 mg/g at pH 6 with adsorbent dose of 0.2 g/L and the adsorption data were well described by the Langmuir isotherm model and the pseudo-first order kinetic model. According to these studies, the HTlc500 has potential application in fluoride ions removal field.

Research Highlights
► The HTlc500 has the largest adsorption capacity at pH 6.
► The adsorption process is well described by the Langmuir isotherm model.
► The pseudo-first order model can accurately describe the adsorption of fluoride.